Effects of isolation and body size on the mating behaviour of the hermaphroditic land snail Succinea putris

We examined the combined effects of isolation and body size on (1) the likelihood of mating, (2) the activity role, (3) the precopulatory behaviour, (4) the copulation duration, (5) the reciprocity of sperm transfer and (6) the number of (reciprocally) transmitted sperm in the hermaphroditic land snail Succinea putris. Also, we assessed the effects of isolation on the sizes of the prostate and albumen gland. In contrast to a previous study, we observed no effect of body size on mating behaviour. However, there were strong effects of isolation: isolated individuals showed increased eagerness to mate, were more likely to adopt the active role and mounted shells of partners more than nonisolated individuals. Moreover, isolated individuals transferred more sperm than nonisolated individuals. Copulation duration and reciprocity of sperm transfer were unaffected by isolation. Isolation resulted in an increase in the size of the prostate gland and a decrease in the size of the albumen gland. We suggest that the motivation to mate after a period of isolation reflects a motivation to donate sperm rather than to receive sperm and that this motivation is regulated by the size of the prostate gland.